An ad hoc network is a type of self-organizing network linked by wired or wireless communication. An ad hoc network is made up of multiple devices having communication functionality. Herein, a device having communication functionality in an ad hoc network will be called a node. Also, each node within an ad hoc network transmits and receives packets by multi-hop communication. Multi-hop communication is a technology that enables communication even between nodes that do not exist within communication range of each other, via another node or nodes that exist within the communication ranges of the respective nodes.
One example of a system utilizing an ad hoc network is a metering system that, by building a node capable of wireless communication into the power meters of respective homes, collects information such as the amount of power consumed by each home via the ad hoc network. In the metering system, a packet that includes the amount of power consumed by each home as detected by each electricity meter are forwarded from each node provided in the electricity meter of each home to an electric power company system. Each node in such a metering system stores personal information related to the power usage of each home in each node's own storage area.
Additionally, from the perspective of anonymity, anti-tampering, and the like, there is demand to conduct secure communication utilizing an ad hoc network. As one example of secure communication, a technique such as encrypting some or all packets for forwarding may be used. In order to conduct secure communication, each node stores information, such as an encryption key for encrypting personal information, in each node's own storage area.
Meanwhile, there is also technology that, when a mobile device senses a designated vibration, enables a device protection function that disables operations other than a designated unlock operation. Additionally, if a legitimate user inputs the unlock operation, the technology disables the device protection function. Such a mobile device is disclosed in Japanese Laid-open Patent Publication No. 2011-30054, for example.